Core structures



Feb. 5, 1957 J. G. FORD CORE STRUCTURES Filed Sept. 25, 1953 INVENTOR Q $0 a u w.

United States Patent CORE STRUCTURES James G. Ford, Sharon; P at, assignor to Westinghouse Electric Corporation, East Pittsburghg' Pa.,--a =corporation of Pennsylvania Application September 23, 1953, Serial No. 381,913- 8 Claims; (C]. 336- -210) The invention relates generally. to'wound cor-e structures, and, more particularly, to the-holding-of the turns of wound cores in the as-wound position.

With theadvent of oriented silicon steel,- in order to take full advantage of the high permeability characteristics of the material, the wound core had to be perfected.

One type oftthewound core involves the cutting of the core into two U-shaped sections in order to fit it around a preformed coil. In this type of core, when it is cut into two U-shaped sections, there is the problem of keeping the turns in the as-Wound position The=usual practice is to impregnate the core as wound-withsuitable resinous material for bondingthe turns to one another.

It has been found that many-types of resins .carrying ahigh percentage of solids gives a good bond which has adequate strength for holding the turns together. However, it has also been found that Whenthe solid content of the resin is something of the order of 18% losses will occur in the core which are undesirable. Tests have revealed that when the solids are somewhat above a figure of about 18%, the losses may beincreased from 10% to If the bonding material consists of a resin having'less than 18% solids, the losses are not great enough to cause any serious concern. However, in the interests of' efiiciency, it is always desirable to reduce the losses as much as possible.

The object of the present invention is to provide members that may be applied in the process of winding a core for holding the turns of the core in the as-wound positions.

It is also an object of the invention to provide metallic members applied during the. winding of a core for holding the turns of the'core inthe as-wound relative positions and which will permit the impregnation of the core with resinous bonding material! Other objects of the invention'will in partbe obvious and in part appear hereinafter.

The invention, accordingly, comprises an article of manufacture possessing the features, properties and the relation of elements Which'willbe exemplified in the article hereinafter described.

For a fuller understanding ofthe'nature and objects of the invention, reference" should'be had to the following detailed description taken in connection with the accompanying drawing, in which:-

Figure 1 is a view in perspective showing how the core is wound, and

Fig. 2 is a view in perspectiveshowing the finished core cut into two U-shaped sections.

Referring now to the drawing and- Fig..il, in particular, a perforated tubular member or a perforated plate folded to simulate a tubular-member, shown generally at 10 has-wound thereon, a plurality of-turns of "oriented sili-' con iron strip11. The number of turnswill depend on the size of core required; Thi'sds'always predetermined When the core is wound, the portionll is usually called the yoke while the portion 13 the leg. In preparing the perforated member 10,'it will-be made of such a length that the portions extendingbeyond the edges of the turns or theends of the coremernber when bent outwardly will reach across the yoke and leg members of the core and present sufiicient material to be bent backwardly across theout'er most turn of the core as best shown in Fig. 2.

In the operation of winding the core, the perforated sheet shown generallyat 10 iswrap'ped around a mandrel disposed for rotation, A collapsible mandrel is preferably employed since it can be readily removed from" the'core when the winding operation has been completed. Theshape and size of the perforated member will be, to some extent, determined by the shape and size of the mandrel which of course will be designed for a predetermined size of core. A collapsiblemandrel is not shown in the drawing since they are well known'in the art.

When the predetermined number of turns have been wound, the strip of oriented silicon steel is cut and the end of the last turn iswelded to the/next mm below.

Then the tubular perforated member may be cutat' the corners to permit the turning or bending of the side members 143 and the end members'lsoutwardly across the leg members 13 and yoke-members 12,'respectively. The end portions of the side and end members 14 and 15 are then folded across a portion of the outermost turn of the core. The length of the members 16 turned across the outermost turn of the core will depend on the designer and the results he is required to obtain.

In selecting the material from which the perforated member or support lll'is made, due consideration must be given to the conditions tobe met. In some instances,

oriented silicon iron sheet maybe employed; When this type of material is utilized, the problem of electrically connecting the edges of the wound core is not as great as when-ordinary iron is employed, since'the oriented silicon iron carries art-insulating film. However, when the holes are punched in the oriented silicon iron, the" insulating film is, to some extent, removedand a problem of inteiposing insulation between the'member 10' and the edges of the wound core may have to be taken care of.

When the insulating member 10 is made from iron, or other metalthat may'electrically connect the edges of the wound core, it is necessary top'rovide means for insulating the member 19 from the core. The best time to apply the insulation is after the perforations "have been made in the sheet metal from which the member 10 is to be formed.

It has been found that a satisfactory method of apply-' ing'the insulation is to-treat one side of the perforated sheet with an adhesive such, alcohol or sodium silicate. The surface may then be sprayed or coated with inert fibers orrefra'c'tory powders.

Considerable success-in insulating the perforated sheets has been had by utilizing-inorganic fibers such as glass or asbestos and refractory powders such as aluminum silicate, aluminum oxide and magnesium oxide. The polyvinyl alcohol or sodium silicate will bond the fibers or powders to the metal'and provide an insulating layer. The thickness of theadhesive andfibers or powders will depend on the conditions to bemet;

While polyvinyl alcohol and sodium silicate have been i atented Feb. 5, 1957 for example, as polyvinyl proposed as adhesives, it will readily be appreciated that many other adhesives and resinous materials well known in the art may be employed for bonding the fibers or powders to the metal sheet. The particular adhesive or resinous material employed will to some extent depend on the fibers or powders employed.

It has been indicated hereinbefore that inorganic fibers and refractory powders have been employed in building up the insulation. However, it is not necessary to limit the adhesives to inorganic materials and good results have been obtained using organic adhesives. In the annealing process, the organic adhesive may be burned out, out the inorganic fibers or refractory powders employed in building up the layer of insulation will remain in place.

After the core has been wound and the trailing end of the oriented silicon iron strip has been welded down or fastened in some suitable manner, the side and end portions 14 and 15 of the perforated member 14} are turned outwardly and folded into the position shown in Fig. 2. The collapsible mandrel hereinbefore described is then removed. The turns of the core are now supported in the as-wound position.

In order to relieve stresses locked in the silicon sheet or strip in the winding operation, the core is annealed. The annealing operation will be carried on in a manner and at temperatures well known to those skilled in this art. The usual practice in placing the cores in the annealing furnace is to stack them on edge and weight them so that the perforated metal members are held tightly against the core and will become set in this position. A core structure of this type has an advantage in the annealing operation in that it may be annealed after the mandrels have been removed.

When the annealing operation has been completed, the cores are next impregnated with some suitable organic resin with a solid content of about 18% or below for the reasons given hereinbefore. Many suitable impregnating compounds are well known in the art. impregnating compounds disclosed and described in applicants Patent 2,623,920, issued December 20, 1952, may be employed. However, it is to be noted that in preparing the impregnating compounds the solid content should be kept at 18% or below.

Experience has revealed that when a perforated member such as 10 is applied to a core in the manner hereinbefore described, the inner turns of the core do not collapse either in the annealing process or afterward. Nor will the outer turns of the core split away. Of course, the designer, in specifying the material for member 10, will have to select material with adequate strength. This presents no problem since the strength of suitable materials is well known.

It has been found that the cores, even after impregnation, have many open capillaries into which water and aqueous solutions will penetrate in further manufacturing operations. In order to prevent the penetration of deleterious matter such as water and aqueous solutions, the core is treated with a hot paraffin to fill all the open capillaries and protect the oriented silicon steel from which the core is wound from oxidation or rust.

In order to cut the core into two U-shaped sections to fit around a preformed coil, 2. Carborundum disc may be employed. It is preferable to cut a core such as shown in Fig. 1 along the line 17 as shown in Fig. 2. In this way, clamping members made from the member 10 are left on each side of the cut. The clamping members in conjunction with the bonding material hold the turns of the two U-shaped members in the as-wound position.

The next step after the core is cut into two U-shaped sections is the grinding and etching of the cut pieces. This is performed in the well-known manner and will not be described in detail. However, it has been found that the parafiin has so filled all the capillaries and crevices in the core that water or other aqueous solutions do not penetrate between the turns of the wound core.

While only one embodiment of the perforated supporting member or unit 10 has been shown and described, it will be readily appreciated that many different types could be designed without departing from the thinking of this invention. For example, two channel members might be fitted over the mandrel and the strip of oriented silicon steel wound around them. This would result in two spaced supporting members which, when turned outwardly, would adequately support the inner turns of the core and hold the outer turns in the as-wound position. Further, it would not necessitate the cutting of the perforated member when cutting the core into two U-shapecl sections.

The perforations in the supporting member 10 are employed to facilitate the impregnation of the core with the bonding resinous materials.

It would also be possible to employ a composition material for clamping the turns of the core in the as-wound position. The only requirement is that the composition be capable of withstanding temperatures. Composition material capable of withstanding temperatures would usually be too expensive and, therefore, have not been mentioned in this specification.

When the U-shaped core members have been prepared they are fitted together in pairs. These pairs of core members are usually fitted over preformed coils in a manner commonly practiced in the art. The U-shaped core section may be held in assembled relationship in any suitable manner as by the use of straps 18.

Since certain changes may be made in the above article and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In a wound core, in combination, a plurality of turns of an oriented silicon iron, a perforated metallic member on which the turns of the core are wound, insulation provided on the perforated metallic member, the insulation being provided on the side of the perforated metallic member which receives the turns of the core, the perforated member being bent outwardly and backwardly to overlap and engage the turns of the core to hold the turns in substantially the as-wound position.

2. In a wound core, in combination, a plurality of turns of an oriented silicon iron, a perforated metallic member on which the turns of the core are wound, insulation disposed between the perforated metallic member and the turns of the core, the ends of the perforated metallic member being bent outwardly and backwardly upon itself to form substantially U-shaped members fitting over and engaging the edges of the core to hold the turns of the core in substantially the as-wound relative positions.

3. In a wound core, in combination, a plurality of turns of an oriented silicon iron, a perforated metallic member, the turns of the core being wound on the perforated metallic member, insulation disposed on the perforated metallic core member to receive the turns of the core, the ends of the perforated metallic member extending beyond the turns of the core, the ends of the perforated metallic member being folded across the turns of the core and backwardly on the turns of the core to hold the turns of the core in substantially the as-wound position, the perforated member .facilitating impregnation of the core with resinous bonding material.

4. In a wound core, in combination, a plurality of turns of an oriented silicon iron strip, perforated metallic members on which the core is wound, insulation provided between the core and perforated metallic members, the perforated metallic members being disposed in contact with the yoke and leg members of the core and extending beyond the turns of the core, the perforated members being folded outwardly across the edges of the turns and backwardly over the turns of the core to form substantially U-shaped members to hold the turns of the core in substantially the as-wound relative positions, the perforated metallic members facilitating the impregnation of the core with a resinous bonding material.

5. In a wound core, in: combination, a plurality of turns of an oriented silicon iron strip, perforated metallic members of substantially channel shape applied to the core to engage and hold the turns of the core in substantially the as-wound relative positions, insulation between the perforated metallic channel members and the turns of the core, the perforations facilitating the impregnation of the core with resinous bonding materials.

6. In a wound core, in combination, a perforated metallic member coated on one side with an insulating material, the perforated metallic member being bent around the core to form a substantially U-shaped member applied over the edge of the core to engage and to hold the turns in substantially the as-wound relative positions, the face of the perforated metallic member carrying the insulation facing the core, the perforations facilitating the impregnation of the core member with resinous bonding material.

7. In a wound core, in combination, a perforated metallic member for receiving a plurality of turns of an oriented silicon iron strip, an insulating material applied to the perforated metallic member on one side to receive the strip from which the core is wound, a plurality of turns of a strip of oriented silicon iron wound on the perforated metallic member, the perforated metallic member extending beyond the edges of the turns which form the ends of the core, the portions of the perforated metallic member extending beyond the turns being folded across the ends of the core and back on the turns forming substantially U-shaped members for holding the turns in substantially the as-wound positions.

8. In a wound core, in combination, a perforated metallic member for receiving a wound core, an insulating material applied to the perforated metallic member on the side disposed to receive the turns of the oriented silicon iron, a plurality of turns of a strip of oriented silicon iron wound on the perforated metallic member, the perforated metallic member extending beyond the edges of the turns forming the yokes and legs of the core, the portions of the perforated metallic member extending beyond the turns being folded across the yokes and legs of the core and back on the turns forming substantially U-shaped members for holding the turns in substantially the as-wound positions, the core carrying the perforated metallic member being impregnated with a resinous bonding material and hot paraffin applied to the core to fill all the capillaries and crevices in the core to prevent entry of deleterious matter.

References Cited in the file of this patent UNITED STATES PATENTS 2,523,071 Somerv-ille Sept. 19, 1950 2,579,560 Ford Dec. 25, 1951 2,623,920 Ford Dec. 30, -2 

